Light-projecting apparatus



July 31, 1923.

D. J. MGCARTHY LIGHT PROJECTINGAPPARATUS- Filed June 28, 1920 Patented July 3l, 19.23.

UNITED STATES PATENT OFFICE.

DANIEL 'l1-MART, 0l;l ELGIN, ILLINOIS, ABSIGNOB. TO CHICAGO RAILWAY SIGNAL AND SUPPLY COMPANY, 0F CLHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

LIGHT-PROJECTING APPARATUS.

Application aled lune 28, 1920. Serial Fo. 392,858.

'To allwlwm it may concern:

Be it known that I, DANIEL J. McCAirrn-r,

a citizen of the United States, residing at Elgin, in the county of Kane and State of Illinois, have invented certain new and useful Improvements in'Light-Projecting A paratus, of which the following is a speci cation.

This invention relates to improvements in light projectin apparatus.

One of the o jects of the invention is to provide an improved meanswhereby the full radiant light energy from a vsource of light ma be projected in parallel rays, directly an indirectly, in a given direction.

Another object is to ather the correlated rays of light, radiating in all directions from a single source, and project them in parallel lines in a concentrated intense beam, and when required, subsequently to spread the rays into a larger beam by use of suitably constructed and arranged lenses, thus rendering the field of illumination correspondinfrly larger and utilizing, in this way, the full light energy of the source ofrlight.

Another object is to provide an improved light reflectn and projecting enclosure within which t e a'rcontalned and by whicha part of the radiant lightis` reflected back thru the source of light, as a focal point, to a parabolic reflector from which it is projected in parallel rays thru an opening in the enclosure. v

The invention broadly considered is a means by which substantially all of the light rays, propagated by a source of light, is rojected as from a parabolic'reflector.

goma of the rays that do not primarily impinge upon the parabolic reflector, are refiected from radial lines thru the focal point, occupied by the lamp, to the parabolic neflector, and thereby projected with the rays thatreach the parabolic reflector direct y from the lam thus intensi ing the beam of projected li ht and directing practically all of the ra iant light energy from the lain into the beam.

T e device may conveniently and economically be used for railway and other signaling apparatus, for railvvr'ay.v and automobile head lights and in othe'sit'uations in which the full effect of a lamp is to be projected in a strong concentrated beam.

Other` further and more specific objects of the invention will become readily appar- Fig. 2 is a similar view of a modified formv of the apparatus.

In both views the same reference characters are employed to indicate similar arts.

In both of these views 5 is an enc osure' havinginternally light reflectin surfaces and each enclosure contains a araolic reflector 6, with a lamp 7 at'the ocal point of the parabolic' reflector. In Fig. 1 the internal reectng surface 8 is a true elli se, or elliptic in form. The focal point o the elliptic reflector and of the parabolic reflector'v coincide at the point at which the concentrated light source is placed corresponding with the lam 7. 10 is an opening in the reflector 9 9 thru which the beam of li ht will pass when projected from the para lic refiector 6.

The many rays of light emanating fro between the two foci of the elliptical reector 8 and perpendicular to its axis.

A ray of light, such as illustrated by the line 11, coming from the lamp 7 and strikin the elliptical surface at 12, will be reflecte thereby at such an angle that when it strikes the reflecting surface 9, as at 13, it will be reflected thereb thru the focal oint, as by line 14, which ocal point is the amp 7, and thereafter strike the parabolic rellector and then it will be projected from the parabolic refiector, in parallel ra s with other similar rays to form a beam of, parallel rays which will pass out from the enclosure by way of the opening 10. The rays of light just referred to will be projected from the parabolic reflector in the saine manner as if it had been sent direct to the parabolic reflector from the lam or li ht source.

By use of the el iptica reflector 8, conjointly with the reflector 9, and in conjunction with the parabolic reflector, the entire radiant energy of the lamp is rojected into a beam of parallel rays roc ing from the enclosure, or device, and therefore the total aov l light.

flux of light from the lamp is concentrated into a beam of the diameter substantially equal to the diameter of the opening 10 and this beam will be many times more intense, or would contain a larger numberv of lightI rays, than would be possible to obtain from the projector or parabolic reflector without the cooperation of the reflectors referred to.

In Fig. 2 substantially the same results are obtained, but by the use of two parabolic reflecting surfaces and a curved surface. In this case 6 and 8 are parabolic reflectors whose focal points are both at thesource 'of The reflecting surface 9 is a curved surface, so arranged that the parallel rays of light striking it from the parabolic reflector 8 are again reflected back thru the focal point and strike the reflecting surface of the arabolic reflector 6, which sends out, in paraqlel rays, a beam of light thediameter substantially equal to the opening 10.

In either case, as illustrated in Figs. 1 and 2, the concentrated beam of light may be spread into a larger beam by the use of a.' lens combination in which the double curved lens 15, which is a type of lens which tends to spread parallel light rays entering it. The lens 16 is interposed between the lenses 15 and 17 to bend the rays the least possible extent, thus producing a highly effcient lens combination.

The line 18 shows the manner in which the beam is broadened after leaving the container 5 from which it is pro'ected. The line 1S represents a single ra o light which is in parallel relation wit other similar rays emanating from the same source, and constituting the beam of projected light.

In each of the structures, illustrated in Figs. 1 and 2, the lamp 7 or 7 is contained within the enclosure providing walls having internally reflecting surfaces. In many instances the lens 15, 16 and 17 will not be required but in the event that they are desirable, they may be employed for the purpose described.

While I have herein shown and described a preferred form, and one modicaton of the device, it is manifest that other variations will readily be suggested, to persons skilled in the art, which will fall within the scripe of the appended claims.

aving described my invention what I claim as new and desire to secure by Letters Patent is:

1. A light projecting device comprising an inner refiector substantially parabolic in form and a cooperating outer reflector substantially elliptic 8 in form in which the focal points of the elliptical reflector and of the parabolic reflector coincide to project llght in the same direction; a source of light at said focal point and an opposing reector arranged to return the light proceedin from the elliptical reflector only, thru sai focal point to the parabolic reflector.

'2. A light projecting device com rising a reector substantially parabolic in orm and a' cooperating reHector substantially elliptic in form in which the focal points of the elliptical reflector and of the parabolic ref'lector coincide; a source of light at said vfocal point and an opposing reflector located in a plane midway between the two foci of the elliptical reflector and perpendicular to the axis of the elliptical reflector, arranged to return the light proceeding from the elliptical reflector, thru said focal point to the parabolic reflector.

lIn testimony whereof I hereunto Subscribed my name.

DANIEL J, MCCARTHY. 

